In FIG. 1 of the above-referenced application and patent, a low power transceiver is disclosed (the Figure shows only the receiver portion) in which a transmitter and receiver operate non-coherently, that is, without the requirement that transmitted and received signals bear a fixed electrical frequency and phase relationship so that as a result, the transceiver can be simple and robust and of lower power consumption. One such embodiment integrates a GPS receiver into an existing primary two-way communications system, which accomplishes position location for its user. Moreover, the resulting position location could be caused to be transmitted automatically or on signal from any other transceiver or ground location using the primary link.
The present invention provides wireless communications capability, for either terrestrial or space based operations, involving the simultaneous processing of multiple communications signals and types, received from various and multiple bands, such as an integrated TDRSS/GPS satellite receiver, as well as numerous other waveform and frequency band combinations. The key features of the transceiver are that it is multi-channel/multi-band, leverages ongoing transceiver technology, is low power, is applicable to both spread and non-spread signals (i.e. applicable to a much broader range of users) and provides high performance, rapid acquisition/reacquisition and tracking in a single digital processing path.
Applications of the invention include integrating GPS into a receiver primarily using another communications link, thus providing receiver position and time across that link; among others, tracking and telemetry for launch vehicles (i.e., range safety) using TDRSS/GPS is a prime example of this. Other applications include integrated GPS/GLONASS, multi-mode analog/digital cellular, integrated NASA/Government communications links (i.e., TDRSS, GN, SGLS, etc.).
The invention is directed to communications system operating in one or more frequency bands comprising a various number of channels per band (for a total of N channels), and transceiver means for receiving these multiple bands of signals characterized in that the transceiver comprises a system of antenna and RF front end for each said band, a separate RF to IF downconverter for each said band, said IF for each band centered at a succession of frequencies Fc such that the spectra for each band are non-overlapping, with said center frequencies and analog-to-digital converter sampling rate chosen such that one band is centered at baseband, and one or more other bands are centered at a specific relationship with the sampling rate such that each band is individually downconverted to baseband by appropriate selection of tap weight multiplying sequences (such as alternating +/xe2x88x92 sequence for the case of Fc equal to one-fourth the sampling rate), combining means for combining said RF signals, analog-to-digital converter means for converting analog signals to digital signals from said combining means, digital downconverter means for converting said digital signals to baseband signals and a single digital processor sequentially time shared among all said Bands and channels, a signal processor connected to said single digital processor responsible for any final signal and/or data processing or formatting, and a signal transmitter of unspecified design details, coupled into the said transceiver antenna path by means of a diplexer device.
Further, the invention also features a tracking and data relay satellite system operating in the S-band (TDRSS) and in conjunction with a GPS satellite system operating in the L-band, and transceiver means for receiving L-band and S-band characterized in that the transceiver comprises a system antenna and RF front end for each said S-band and L-band signal, a separate RF to IF downconverter for each said S-band and L-band signal, said IF for said S-band signal operating at a frequency Fo and said IF signals for said L-band operating and centered at a frequency Fo plus a predetermined separation frequency so that the spectra for said S-band and the spectra for said L-band are non-overlapping, combining means for combining said IF signals analog-to-digital converter means for converting analog signals to digital signals from said combining means, digital downconverter means for converting said digital signals to baseband signals and a single digital processor sequentially time shared among said S-band and L-band signals, respectively, a GPS navigation processor and a TDRSS data processor connected to said single digital processor, a TDRSS (S-band) signal transmitter of unspecified design details, coupled into the said TDRSS (S-band) transceiver antenna path by means of a diplexer device.
Furthermore, invention also features a multi-Band, multi-channel digital matched filter (DMF) implementation comprising multiple sets (N) of PN-Generators and storage means for maintaining N sets of tap weights within the DMF, N-stage data delay line which shifts the digital data samples down the line at the baseband sampling rate, arithmetic circuitry for multiplying alternate taps of said delay line by one of the stored sets of tap weights, pre-multiplied by the +/xe2x88x92 or other appropriate downconversion sequence, and summing each of said products, to form a correlation output sample that is a member of the sequence corresponding to a the channel represented by the selected tap weights; sufficient consecutive such sum-of-products samples are thus formed to form the complete correlation epoch function corresponding to the selected channel, whereby during acquisition, the tap weights for a single channel are manipulated appropriately such that consecutive DMF output samples represent correlation epochs associated with a particular PN alignment (offset), and thus an acquisition detection circuit can observe which of the correlation alignments is of sufficient magnitude to indicate the correct PN alignment, and thus transition that channel into tracking, and during tracking, the tap weights are alternated between various channels and manipulated appropriately such that the output sequence from the DMF thus consists of a sequence of sum-of-products samples that are in fact also a sequence of correlation epochs corresponding to each of the channels being tracked, and during ongoing operations in fact both acquisition and tracking operations among multiple channels may be simultaneously taking place using the said techniques.